Double sheet detector for printing press



y 1965 R L. MIASKOFF -ETAL 3,185,473

DOUBLE SHEET DETECTOR FOR PRINTING PRESS Filed June 25, 1962 INVENTORS.Jim/aw M/ASKOFF FEE/25mm L. ARA/m United States Patent 3,185,473 DOUBLESHEET DETECTOR FOR PRINTING PRESS Leonard Miaskolf, Flushing, andFrederick L. Warner, Brooklyn, N.Y., assignors, by mesne assignments, toFairchild Camera and Instrument Corporation, a corporation of DelawareFiled June 25, 1962, Ser. No. 205,001 3 Claims. (Cl. 27156) Thisinvention relates to sheet feeding machines and more particularly itrelates to improved means to detect double sheets and divert them fromthe normal feed path.

The need for a double sheet detector mechanism to prevent the feeding ofdouble sheets is well known in the art. For example, when double sheetsare fed to a printing press the inked image will be transferred to onlyone of the sheets. This transferred image is usually of a poor qualitydue to the increased pressure exerted upon the printed sheet by theprinting cylinders. The pressure exerted by the printing cylinders isset for individual sheets and is a significant factor in obtaining asharp and clear product. If double sheets are fed this pressure willincrease and the transferred image will be blurred. It is thus apparentthat. many sheets would be improperly printed if provision is not madeto prevent doubles from being fed. Moreover, the pile of printed sheetswill have blank sheets intermingled therebetween.

In todays sheet feeders the problem of feeding doubles is stillimmediate in the art, although sheet separating means are inuse to tryand insure against feeding doubles. The problem is particularlyaccentuated in automatic high speed suction feeders that are designedfor general all purpose operation with different types and sizes ofsheet stock. In a usual, case when the operating level of the top sheetof a pile is set high, the level being determined by the type anddimensions of sheet stock used, suction feeding means usually embodiedin the form of a reciprocating suction foot may intermittently feeddoubles.

Heretofore devices were used to detect sheet doubles but they were notpositively synchronized with the sheet feeding device. Thus when adaptedto be used in higher speed sheet feeders they were too slow in responseand allowed doubles to be fed to the printing press.

- It is therefore an object of the present invention to provide animproved double sheet detector mechanism adapted especially for use ingeneral purpose high speed sheet feeders.

In the present invention there is provided in a sheet feeding machine anadjustable sheet detector mechanism that allows single sheets to passfreely thereunder, but detects double sheets and actuates a deflectorplate mechanism positively synchronized with the feeding device thatejects the double sheets to .a .sheet holder. More specifically, boththe sheet feeder and the detector plate mechanism are driven by acontinuously actuated drive shaft that times the sheet feeding cycle Byadapting the deflector plate mechanism to be actuated by this shaft thedefiector plate can be pivoted to an ejecting position with a minimum oftime delay after the detection of double sheets.

Features and advantages of this invention may be gained from theforegoing and from the description of a preferred embodiment whichfollows.

In the drawing:

The figure is a side elevation of a feeding machine showing the improveddouble sheet detector mechanism of the present invention.

Some of the elements in the figure are shown in diagrammatic form asthey are of the type commonly used in the art and are only ancillary tothe present invention.

In the figure of the drawings there is shown a sheet feeding apparatus10 embodying the double sheet detector of the present invention. Theapparatus selected for illustrative purposes is a suction feeder havinga suction foot 11 which is pivotally fastened to an arm 13 which in turnis pivotably supported on shaft 14. Arm 13 is provided with a camfollower 15 that engages a cam 16 keyed to a shaft 17. This latter shaftis continuously rotated so that cam 16 pivots arm 13 downwardly to lowersuction foot 11 into proximity with the top sheet of a pile A. As arm 13is pivoted upwardly the suction foot lifts the top sheet from the pile.At this time a cam 18 also mounted on shaft 17 pivots suction foot 11forwardly to present the sheet to a pullout roller assembly 20. Afollower 21 rotatably mounted on suction foot 11 is the means wherebycam 18 advances the suction foot and the sheet carried thereby to thepullout roller assembly 29. For clarity, in the drawings only the lowerroller 22 has been shown.

The operating height of the pile A can be set so that elevator mechanism25 driven by a chain drive (not shown) automatically rises to maintainthe top sheet of the pile at a predetermined level. This level dependsupon the type of stock used and, as for example, when a heavy stock isused this level is set high and the probability of feeding double sheetsto the pullout roller assembly is greatly increased. After a sheet isdelivered to pullout roller assembly 29 it is translated thereby to aconveyor table 26 which translates the sheet to a printing press (notshown). In the embodiment shown glass marbles 28 are mounted in frame 29and provide means for pressing the sheets against an intermediate driveroller 30. The pullout roller assembly comprises a plurality of upperpullout rollers and a lower pullout roller 22. The latter roller issecured to a driven shaft 31 and is driven thereby at a constant speed.Lower roller 22 which preferably extends across the width of the feedingapparatus is generally made of metal and may have its surface knurled toprevent sheet slippage.

Mounted in association with the lower pullout roller is a detector footmechanism 32 that, when double sheets are fed, actuates a deflectorplate mechanism 33 to deflect the sheet doubles to a holder (not shown).The detector foot mechanism 32 has a recessed body housing disposed toengage cross bar 35 by means of a wedge block 36.

' The cross bar is secured in the side walls of the machine.

A detect-or foot 38 is rotatably mounted at the lower end of a clevisassembly 39. The assembly is threaded into fixed engagement with an endportion of a shaft 40, which is mounted in the body housing. A spring 41secured to clevis assembly 39 and detector foot 38 is provided to urgedetector foot 38 to a detecting position in contact with a restrainingpin 45, fastened to the top of the clevis assembly. When double sheetsare fed, detector foot 38 is rotated clockwise (as shown) against theurging of spring 41. The detector foot is also provided with an ear 46that 'has a lateral projection 47 adapted to be engaged by a lateralprojection on the deflector plate mechanism as will be described later.A compression spring 49 mounted in the housing reacts against an end ofshaft 40 and urges clevis assembly 39 and detect-or foot 38 downwardly.Shaft 46 is provided with a threaded hole 5%) into which the tip of aspindle 52 is threaded, The remote end of the spindle has a knurledadjustment nut 53 and a graduated indexing wheel 54 secured thereto. Thegraduated wheel is resiliently urged into engagement with the top ofbody housing 34 by the downward urging of compression spring 49.Graduated wheel 54 is positively engaged by an index finger 56, securedto the body housing by means of machine screws 57. By turning adjustmentnut 53, spindle 52 causes shaft 40 to translate and thereby changes theclearance of single sheet position of detector foot 38. This amas /3indexing device allows an operator to set the mechanism for a fine andaccurate clearance adjustment of the detector foot in reference to thelower pullout roller 22. Machine screws 57 in addition to securing indexfinger 56 to the body housing, also secure two tusk shaped guide fingers58 thereto. These fingers are adapted to help guide sheets with upcurledlead edges into the pullout roller assembly.

Cross bar 35 has a sloping surface 60 which is engaged by wedge block 36mounted at the end of a thumb screw 61 which can turn in the block. Thescrew is threaded through an upper arm bracket 62 of the body housingand as it is threaded downwardly it locks the bracket to cross bar 35.When the thumb screw is loosened, the detector foot mechanism can bepositioned along the cross bar to accommodate paper stock of diflerentwidths.

In practice the detector foot is adjusted by turning thumb nut 53thereby raising and lowering the detector foot so as to have a clearancespace which will permit a single sheet to pass freely but which will beengaged by a double sheet and rotated clockwise. If, however, theaggregate thickness of double sheets is greater than the set clearance,jamming will be prevented inasmuch as the double sheet can raise thedetector foot against the compressive force of spring 49. The lowerpullout roller 22 is driven at an appropriate speed so as to be able todrive double sheets against the frictional drag of the detector foot.

Deflector plate mechanism 33 is provided with a bell crank member 64pivotally mounted on the machine frame. Bell crank 64 consists of threearms, as shown, and is resiliently urged in a counter-clockwisedirection by means of a coil spring 65. The first arm 66 is providedwith a cam follower roller 67 adapted to engage the periphery of a cam68 and be driven thereby. The periphery of cam 68 comprises two arcuatesections 69 and 70 merged together by two straight line segments.Section 69 is of larger radius than section 70. The cam is keyed toshaft 17 and driven clockwise thereby. Shaft 17 also drives suction foot11, as above described, and it is for this reason that the operation ofthe suction foot and the double sheet detector can be positivelysynchronized. The second arm 71 has a lateral projection 72 formed atits remote end adapted to engage the lateral projection 47 formed ondetector foot 38 while the third arm 74 has a connection lever 75pivotally mounted at its remote end. The lever is rotatably mounted ondeflector plate 77 and is capable of having its length varied by meansof adjustment screws. The deflector 77 is rotatably mounted on a pin 78and is rotated to a sheet ejecting position when bell crank memberpivots counter-clockwise. When follower roller 67 rides on section 69 ofcam 68 there is a slight clearance between the lateral projection on arm71 and detector foot 38, and when an individual sheet is correctly fedthe lateral projections engage and cam follower 67 is prevented fromengaging section 70 of cam 68. When double sheets are fed as seen in thefigure, detector foot 38 rotates clockwise and cam follower 67 remainsin engagement with the periphery of cam 68 causing bell crank member 64to rotate counter-clockwise and deflector plate "77 to pivot to anejecting position.

In operation, shaft 17 rotates clockwise causing suction foot 11 todescend upon the top sheet of pile A, lift and feed it to the pulloutroller assembly. During this operation, follower roller 67 rides onsection 69 of cam 68.

If a double sheet is fed, detector foot -38 is driven clockwise againstthe urging of spring 41 by the double sheet. Thereafter cam follower 67rides down from section 69 to section 79 of cam 68. This causes bellcrank 64 to pivot counter-clockwise and deflector plate 77 to move toits ejecting position where the double sheets drop by gravity to thesheet holder. Before the next sheet feed cycle, follower =roller 67engages the section 69 of cam 68 and returns the deflector plate to itssheet supporting or normal operating position. Spring 4-1 then pivotablyreturns detector foot 38 to its operating position in engagement withpin 45. If then an individual sheet is correctly fed, detector foot 38remains in its single sheet position and follower roller 67 is preventedfrom riding on section of cam 68 by the engagement of the lateralprojections 72 and 47. The deflector plate therefore remains in itssheet supporting position and the sheet passes unhindered to theconveyor board.

It is to be understood that many changes can be made in the disclosedembodiment without departing from the spirit and scope of the inventionand therefore the description and drawings are to be interpreted in anillustrative rather than a limiting sense.

What is claimed is:

1. In a sheet feeding machine having a drive shaft for timing andcontrolling the feed of sheets, a double sheet deflector apparatuscomprising, a sheet deflector plate, bell crank means for moving saidplate between a sheet supporting and a sheet deflecting position, a camthat is continuously rotated to move said bell crank means and saiddeflector plate to a sheet supporting position, spring means for urgingsaid bell crank means and said deflector plate to a sheet deflectingposition, a pivotally mounted detector foot having means for blockingthe spring urged movement of said bell crank means and said deflectorplate, and a spring for maintaining said detector foot in a blockingposition when a single sheet is fed but which permits said foot to bepivoted out of blocking position when a double sheet is fed whereby saidspring means moves said bell crank means and said deflector plate to asheet deflecting position.

2. A double sheet deflector apparatus according to claim 1 wherein saidrotatable cam is mounted on the drive shaft which times and controls thefeed of sheets whereby movement of the bell crank means and the sheetdeflector plate to a sheet deflecting position is timed with the feed ofdouble sheets.

3. A double sheet deflector apparatus according to claim 2 includingadjustable mounting means for the detector foot whereby the single sheetposition of said detector foot can be varied and set in accordance withthe thickness of the sheets being fed.

References Cited by the Examiner UNITED STATES PATENTS 765,414 7/04Dexter 271-56 2,175,167 10/39 Davidson 271-56 X 2,178,713 1 1/39 Wood eta1 27=1-56 X 2,721,737 10/5 5 Hammer et a1. 27=156 X 2,890,884 6/59Mestre 27156 SAMUEL F. COLEMAN, Primary Examiner.

ROBERT A. LEIGHEY, LOUIS J. DEMBO, Examiners.

1. IN A SHEET FEEDING MACHINE HAVING A DRIVE SHAFT FOR TIMING ACONTROLLING THE FEED OF SHEETS, A DOUBLE SHEET DEFLECTOR APPARATUSCOMPRISING, A SHEET DEFLECTOR PLATE, BELL CRANK MEANS FOR MOVING SAIDPLATE BETWEEN A SHEET SUPPORTING AND A SHEET DEFLECTING POSITION, A CAMTHAT IS CONTINUOUSLY ROTATED TO MOVE SAID BELL CRANK MEANS AND SAIDDEFLECTOR PLATE TO A SHEET SUPPORTING POSITION, SPRING MEANS FOR URGINGSAID BELL CRANK MEANS AND SAID DEFLECTOR PLATE TO A SHEET DEFLECTINGPOSITION, A PIVOTALLY MOUNTED DETECTOR FOOT HAVING MEANS FOR BLOCKINGTHE SPRING URGED MOVEMENT OF SAID BELL CRANK MEANS AND SAID DEFLECTORPLATE, AND A SPRING FOR MAINTAINING SAID DETECTOR FOOT IN A BLOCKINGPOSITION WHEN A SINGLE SHEET IS FED BUT WHICH PERMITS SAID FOOT TO BEPIVOTED OUT OF BLOCKING POSITION WHEN A DOUBLE SHEET IS FED WHEREBY SAIDSPRING MEANS MOVES SAID BELL CRANK MEANS AND SAID DEFLECTOR PLATE TO ASHEET DEFLECTING POSITION.